I have the inkling that Hail is going to be much more dangerous later on, once people start to really take advantage of it. Last round, some voters (me included) thought that Cresselia wasn't too bad, but once people started taking advantage of all her duckly attributes, that's when she became dangerous.
Something that just hit me is that Hail is going to make defensive / semi- / Stall teams much harder to create, and the general lack of bulky Pokemon in the tier (excluding Cresselia) makes life even harder. The hail damage cancels out the Leftovers, and makes it easier to wear the walls down. I think this side-effect is really important, because then it causes the tier to be more offensive, similar to what Nidoqueen did, although probably not to that extreme. The direct effect of Hail, itself, isn't all that dangerous, it's the side-effects that are. Of the defensive Pokemon, the one that doesn't care if Clefable and Walrein, thanks to Magic Guard and Ice-typing, respectively. All the others generate chip damage. Now the question is to what extent is this going to happen, probably less than Nidoqueen, but nevertheless at least some. Do we want a balanced metagame? Sure why not. Cresselia is overcentralizing in that she can be half a Stall team herself. I think its important for people to think down the road, and see all the effects of Hail. Blizzard will be more common. Other weathers to cancel Hail. Defensive Pokemon that go more offensive due to Leftovers being canceled out. There's probably more, but I'm only one person. Something for people to think about.
Honestly, that is rather debatable. The lack of Leftovers recovery isn't much though, but defensive Pokemon may still stand. Hail isn't a common sight on the battlefield, really, because they suffer from too much compounded weakness to Fighting and Stealth Rock, which means Poliwrath can stop hail teams cold most of the time. Hail has numerous issues: Firstly, it has to rely on the mighty Snover. That is bad. When you're forced to rely on a mediocre Pokemon like the Mighty Snover, that's a big crutch. Also, very few can take advantage of hail, and those who can are usually Stealth Rock weak, racking up Stealth Rock damage too easily. The impact Hail is making on this meta is not much. Stallrein and Mandibuzz can be very annoying, and Rotom-F and Glaceon can be super powerful, but you must keep in mind that they are Stealth Rock weak and they have the mass weakness to Fighting, plus they are extremely dependent on the Mighty Snover to be successful. Hail is not that good of a weather and is typically not hard to counter. It's not ban worthy.